Pressure-control circuits for gas-type circuit interrupters



G. J. EASLEY May 25, 1965 PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUITINTERRUPTERS Filed Oct. 12, 1961 3 Sheets-Sheet 1 PRESSURE SWITCH(NORMAL PRESSURE CONDITION) .l. 0- CST 99 l l I Fig. INVENTOR Gilbert J.Eosley BY (Z2: M ATTORNEY WITNESSES May 25, 1965 G. J. EASLEY 3,185,895

PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUIT INTERRUPTERS Filed Oct.12, 1961 3 Sheets-Sheet 2 Fig. 2

83 68 w Fig. 3 f

k J 79 80 i I 8| I 83 PRESSURE SWITCH lov 5 y 1965 G. J. EASLEY3,185,895

PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUIT INTERRUPTERS Filed Oct.12, 1961 3 Sheets-Sheet S PRESSURE SWITCH Fig. 4

United States Patent 0 PRESSURE-CONTROL CIRCUITS FOR GAS-TYPE CIRCUITINTERRUPTERS Gilbert J. Easley, Edgewood, Pin, assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a

corporation of Pennsylvania Filed Oct. 12, 1961, Ser. No. 144,705 9Claims. (Cl. 317-59) The present invention relates broadly topressure-control circuits for gas-type circuit interrupters and, moreparticularly, to a pressure-control circuit for a gas-type circuitinterrupter utilizing a minimum number of pressure switches.

As Well known by those skilled in the art, certain gastype circuitinterrupters depend upon their interrupting integrity upon the pressurecondition of the arc-extinguishing gas present within the sealedinterrupting casing. For example, in a gas-type circuit interrupter,such as that set forth in United States patent application filedNovember 18, 1959, Serial No. 853,974, by Robert L. Hess, James M.Telford and Gilbert J. Easley, now United States Patent 3,114,815,issued December 17, 1963, and assigned to the assignee of the instantapplication, there is disclosed and claimed a novel type ofcircuit-interrupting structure in which a puffer element is moved withthe movable contact structure to inject a blast of arcextinguishing gasinto the arcing region. Such areextinguishing gas is completely enclosedin a surrounding casing, within which the separable contacts of thebreaker are disposed and actuated. A sealed drive shaft extendslaterally out of the pressurized casing for the interrupter; andmechanical opening and closing motion is transmitted into the interiorof the sealed casing by means of the drive shaft. As a result,opening ofthe circuit interrupter of the aforesaid application is effected byrotation of the aforesaid drive shaft, which not only effects contactseparation within the pressurized enclosure of the interrupter casing,but also mechanically effects driving motion of the puffer element toinject a gas blast through a suitable orifice and into the arc to effectthe extinction thereof. In such a type of circuit interrupter it isnecessary to maintain a minimum pressure of the arc-extinguishing gaswithin the circuit-interrupter casing.

If the pressure of the gas within the interrupting casing drops below aminimum value, opening of the breaker under such conditions ishazardous; and, in addition, closing of the breaker may result inconsiderable free arcing during such a closing stroke. It is, therefore,desirable to sense the pressure conditions within thecircuit-interrupter casing, and should the pressure drop too low, toprevent closing and tripping of the breaker. At the option of theutility customer, tripping of the breaker may be obtained as thepressure conditions drop to the lower hazardous value.

It is, therefore, a general object of the present invention to providean improved gas-type circuit interrupter in which control is obtainedover the operating conditions of the breaker dependent upon the pressureof the arcextinguishing gas within the interrupter casing.

A more specific object of the present invention is to provide animproved pressure-control circuit for a gastype circuit interrupter inwhich a minimum number of pressure switches are employed for effectingthe desired control.

It is known that, since a definite minimum operating gas pressure isestablished on gas breakers below which the breaker should not beoperated, it is desirable to provide pressure operated switches toperform three functions when minimum operating pressure is reached:

(1) Energize an alarm or warning light to Warn the operator of anabnormal condition.

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(2) Open the closing control circuit of the operating mechanism toprevent closing or reclosing the breaker.

(3) Open the trip circuit of the operating mechanism to prevent trippingthe breaker, or, at the utility customers option, automatically trip thebreaker open.

Generally, these functions are performed by separate pressure switches,but the present invention is particularly concerned with providing animproved control means for performing all three functions with only asingle pressure switch. Since expensive temperature-compensated(density) pressure switches must be used on sealed gas breakers, it isvery desirable to limit the number of pressure switches used.Accordingly, it is a further object of the present invention to providean improved, simplified and dependable pressure-control circuit for agas-type circuit interrupter in which many of the various functions forcontrolling the breaker may be obtained utilizing only a single pressureswitch.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings, inwhich:

MG. 1 is a diagrammatic control scheme for a gas-type circuitinterrupter showing an application of the principles of the presentinvention, the contacts of the interrupter being illustrated in theclosed latched position, and a normal pressurized condition beingpresumed to exist within the pressurized interrupter casing;

FIG. 2 is a side elevational view, partially in vertical section, of asingle pressure switch utilizing micro-switch contact structure suitablefor use in the pressure control scheme of FIG. 1;

FIG. 3 is a fragmentary schematic circuit illustrating a modification ofthe pressure-control circuit of FIG. 1, wherein the low pressure cutoutfor the closing control functions at minimum operating pressure insteadof at the alarm pressure, the micro-switches of the pressure switchbeing adapted for differential pressure operation; and

FIG. 4 is a fragmentary schematic view of a modified type of pressurecontrol scheme associated with the same type of gas circuit interrupteras shown in FIG. 1, again the contact structure being assumed to be inthe closed latched position, and normal pressure conditions existingwithin the sealed interrupter casing.

Referring to the drawings, and more particularly to FIG. 1 thereof, thereference numeral 1 generally designates a gas-type circuit interrupter.As shown, the gastype circuit interrupter 1 generally comprises contactstructure 2 separable within a pressurized casing 3. Preferably, thecasing 3 is filled with a suitable arc-extinguishing gas, such assulfu-r-hexafluoride (SP gas at a suitable pressure, say 45 p.s.i.g.

Opening separating motion of the movable contact 5 toward the right, asviewed in FIG. 1, away from the relatively stationary contact 6 iseffected by a rotatable drive shaft 7, connected by a linkage 8 to amovable insulating puffer cylinder 9 slidable over a fixed cylindricalinsulating guide ltl affixed to the breaker casing 3 by a support 11. Arelatively fixed piston 12 is provided, which cooperates with themovable operating puffer cylinder 9 to effect a compression of gaswithin the region 13. It will be obvious that pressure arising withinthe region 13 will cause an ejection of arc-extinguishing gas outthrough the orifice opening 14, associated with an orifice structure 15movable with the movable contact 5 by a spider member 16. The directionof the flow of gas out through the orifice opening 14 is indicated bythe arrows 17.

The casing 3 generally comprises a grounded intermediate metallicsupported portion 18 and a pair of coextensive insulating cylindricalcasings 19, 20 as set forth more in detail in the aforesaid patentapplication. Preferably, the insulating casings 19, 2.0 are composed ofa suitable Weather-proof material, such as porcelain. An

outer corrugated surface, comprising a plurality of petticoats 21, maybe provided, as well known by those skilled in the art.

The relatively stationary contact 6 is electrically connected to theleft-hand line terminal 22, which is preferably connected to atransmission-line connection L The movable contact 5 is electricallyconnected to a movable guide-rod portion 23 which is guided bystationary fingers, not shown, which are electrically connected to therighthand line-terminal 24. A transmission-line connection L may beconnected, by suitable connector means, to the terminal 24, as shown.

From the foregoing description it will be apparent that in theclosed-circuit position of the circuit interrupter 1, as shown in FIG.1, the electrical circuit traversing the same comprises line connectionL line-terminal 22, relatively stationary contact 6, movable contact 5,movable guide-rod portion 23, relatively stationary fingers (not shown),line-terminal 24 to line connection L To effect opening and closingrelative motion of the drive shaft 7, which extends by way of a sealedconnection externally of the pressurized casing structure 3, there isprovided an operating mechanism, generally designated by the referencenumeral 26. As shown, the operating mechanism 26 is of the pneumatictype, but it could be of the solenoid type, as well understood by thoseskilled in the art. As shown in PEG. 1, the externally-extending portion7A of the drive shaft 7 has affixed thereto a crank-arm 27. Pivotallyconnected, as at 28, to the crankarm 27 is an operating rod 29'connected to a piston 3d at its lower end. The piston 39 moves within apneumatic cylinder 31 by application of gas pressure, such as air underpressure, applied to its lower surface. Preferably, a source ofcompressed gas 32 is provided, and the admittance of this compressedgas, such as compressed air, to the region 33 below the piston 3% iscontrolled by an operating valve 34. The operating valve 34 has adoubleacting valve structure 35 controlled by an armature 36 energizedby a closing coil 37. The closing coil 37 is connected by a circuit 38through the norma1ly-open contacts 39 of a closing relay X. The otherside of the normally-open contacts 39 of the relay X is connected, by aconnection 419, to a terminal 41. The terminal 41 is connected to apositive source of voltage 42, which is located in proximaterelationship to the operating mechanism 26 at the breaker 1. This iscontrasted with a positive source of voltage 43, which is remotelylocated at the station house, which may be at a considerable distancefrom the circuit breaker 1. The negative points of both voltage sources42, 43 are connected to ground, as shown.

As shown in FIG. 1, an accelerating compression spring 45' is providedto bias the drive-shaft 7 in a circuit-opening direction. The circuitinterrupter 1 is maintained in a closed position by a latching device46. The latch 46 may be released by energizing a tripping coil 47, whichenergizes an armature 4s controlling a release rod 49. Thus, energizingthe trip coil 47 results in releasing the latch 46, and permitting theaccelerating spring 45 to drive the crank-arm 27 in a clockwise openingdirection, as viewed in FIG. 1, separating the movable contact structure5, 6 and effecting the extinction of the established are by a blast ofarc-extinguishing gas out through the orifice opening 14, as indicatedby the arrows 17.

In connection with the opening operation it will be observed that theregion 33 below the movable piston St? is dumped to atmospheric pressureby the lower valve element 35a, which opens an exhaust opening 56.Energization of the closing coil 37 will reverse the illustratedposition of the double-acting valve 35 closing the exhaust port 5t) andopening the inlet port 51 admitting thereby high-pressure gas, such ascompressed air, through an inlet pipe 52 and into the region 33 belowthe piston 30 to drive the same upwardly to the closed position of thebreaker 1. The contact structure is maintained in the closed position bythe latch rod 49 moving under the latch nose 4-6 to maintain the breakerin the latched closed position.

As shown in FIG. 1, an anti-pumping relay Y is provided having a coil 53connected in a circuit $4, which includes a low-pressure cut-off LPC. Inaddition, the coil 53 for the anti-pump relay Y is connected, by aconnection 55, through auxiliary contacts 56 associated with theoperating rod 29. The other side of the auxiliary contacts 56 isconnected, by a connection 57, to a ground terminal 53. The groundterminal 5% is also connected to one side of normally-open contacts 59of the relay Y. As shown in FIG. 1, one side of the coil 60 of theclosing relay X is connected through normally-closed contacts 6.1 to aterminal 62. The terminal 62 is connected to normally-open contacts 63,64 of the X and Y relays. As shown, one side of the closing coil 37 isconnected through normally-closed contacts 65 to a ground terminal 66.One side of the tripping coil 47 is connected through auxiliary contact67 to a ground terminal 68, the latter being connected throughnormally-open contacts 69 of the closing relay X.

An important feature of the present invention is a provision of a singlepressure switch, generally designated by the reference numeral 7t), forsensing the pressure P within the casing 3, and actuating a pair ofsingle-pole single-throw micro-switches, generally designated by thereference numerals 71 and 72. The micro-switches 71, 72 may be of thesnap-acting type well known in the art, as for example, the type shownin McGall Patent No. 1,- 960,020, issued May 22, 1934. A pair ofmetallic strips 73, serving as common terminals, may be actuated byplungers '74- to effect contact with normally-closed contacts 76, 7'7,or normally-open contacts '78, '79. The plungers are responsive to anoperating rod 80, which, in turn, is responsive to a diaphragm 81responsive to the pressure P within a container 32 having a pressureconnection 83 with the casing structure 3, as shown.

FIG. 2 more clearly shows the general type of pressure switch re, withwhich the present invention is concerned. With reference to FIG. 2, itwill be observed that the pressure switch 7% generally comprises ahousing 85 containing a terminal block 3:: and a rotatable actuatingplate 87. The actuating plate 87 rotates about a fixed axis 88, and isbiased in opposition to the pressure plunger '74 by a helical coilspring 89. A spring adjustment 9%) may be provided for a fine setting ofthe pressure plate 87 for causing actuation of the micro-switches 71, 72(only one being observable in FIG. 2).

This general type of pressure switch is supplied by the United ElectricControls Company of W atertown, Massachusetts, and is similar to theirtype M27CD. This switch is a temperature-compensated pressure switch,measuring the density, but the temperature-compensating bulb is omittedfrom FIG. 2 of the drawings since it forms no part of the presentinvention and is merely a compensating device.

With reference to FIG. 1 of the drawings, it will be noted that thefirst normally-open contact 79 of the microswitch 72 is connected, by aconnection 91, to an alarm device 92, comprising one or more alarmelements d3, 94. The other side of the alarm elements 93, 94 areconnected to a terminal 95, which is at the potential of the positiveside of the source 43.

A transfer switch 96 is provided having a pair of s ngle-polesingle-throw switch elements 97, 93 the functron of which will be moreapparent from the description to be presented hereinafter.

As shown in FIG. 1, a tripping switch CST is provided connected tothesecond normally-closed contacts 76 of micro-switch '71 and also to thecontacts 97 of the trans fer switch 95. The tripping switch CST has itsother side connected to the positive terminal 99 of the remote source ofvoltage 43.

A closing switch CSC is provided having one side there- .structure 3 toa hazardous value.

ansaese of connected to the positive terminal 99, and having the otherside thereof connected by a connection 1% to the normally-open contacts64 of the anti-pump relay Y and to the auxiliary contacts 161 associatedwith the operating rod 29 of the operating mechanism 26.

The opening operation of the circuit interrupter 1 will now bedescribed. With the transfer switch 96 in the open position, as shown,tripping of the breaker may be effected by closing the tripping switchCST. This will energize the tripping coil 47 through the secondnormallyclosed contacts 76 of micro-switch 71. and through the closedauxiliary contacts 67 of the operating mechanism 26. The energization ofthe tripping coils 47 will cause releasing movement of the latch rod 49to permit the accelerating spring 45 to move the crank-arm 2 7 in aclockwise direction to effect thereby opening of the breaker in themanner previously described. The region 33 within the pneumatic cylinder31 will be exhausted at this time, and will, consequently, offer noopposition to the opening movement of piston 30.

To effect the closing operation of the interrupter, it is merelynecessary to press the closing button CSC. This will energize theclosing relay X through the now normally-closed contacts 101, throughthe low-pressure cutout contacts LPC, through the normally-closedcontacts 61 of relay Y and the first normally-closed contacts 77 ofmicro-switch 72 to the negative side of source 43. The closing of theclosing relay X will eifect closing of the contacts 39 thereof and thiswill energize the closing coil 37 of the double-valve device 35. Openingof the inlet port 51 and closing of the exhaust port 50 will pressurizethe region 33 below piston 30 and effect upward driving movement thereofwhich will correspondingly effect counterclockwise rotation of thecrank-arm 27 and closing of the circuit interrupter 1. The latchingdevice 46 will latch the breaker in the closed position, as shown inFIG. 1 of the drawings.

It will be apparent that if the pressure conditions P within the casingstructure 3 drop to a dangerous or hazardous value, then the pressureconnection 83 of the pressure switch 70 will reflect this low pressurevalue and cause lowering of the actuating plunger 74 of microswitches71, 72 to effect closing of the second and first normally open contacts78, 79 respectively, and opening of the companion second and firstcontacts 76, 77 respectively. This will prevent energization of theclosing relay X and will sound the alarm device 92. In addition, theopening of the contact 76 of micro-switch 71 will open the trippingcircuit to the tripping coil 4-7 by Way of the tripping button CST, sothat it will be impossible for a Serviceman to close the tripping buttonCST and thereby energize the tripping coil 47 to trip the breaker open,if it has previously been closed.

For certain applications it may be desirable to trip the breaker openwhen the pressure P decreases in the casing To perform this function,the transfer switch 96 may be closed. Assuming that the transfer switch96 is closed, the closure of second normally-open contact 78 ofmicro-"switch 71 upon a lowering pressure P will energize the trippingcoil 47 through the now closed contacts 98 of the transfer switch 96. Asa result, automatic tripping of the breaker 1 will ensue upon such alowering of the pressure P. The customer then will have this option byclosing the transfer switch 96 or leaving it open according to hisdesires.

From the foregoing it will be apparent that all three of the functions,namely energizing the alarm circuit, opening the closing control circuitand opening the tripping circuit would normally take place at the samepressure. However, the supplier for this type of switch ,states that itis possible to provide independent pressure control for each single-polesingle-throw switch without increasing the cost. Using such anarrangement,

namely having micro-switch 72 operate prior to microswitch 71, this willenable the alarm circuit to function,

say at 5 p.s.i. above the minimum operating pressure for tripping, whichwould probably be desirable to most customers.

Again using the differential pressure setting between the micro-switches7'1, 72 and assuming that customers insist on low-pressure cutout forthe closing control functioning at minimum operating pressure, insteadof at the alarm pressure, this may be accomplished by adding aninexpensive protective relay 102 instead of providing another expensivepressure switch. Such an arrangement is illustrated in FIG. 3 of thedrawings, which is to be considered in conjunction with FIG. 1 thereof.Here again, the micro-switch 72 is set to function at substantially 5p.s.i. above the operation of micro-switch 71. Upon a lowering ofpressure P, the micro-switch 72 will operate first. This will operatethe alarm devices 92 upon closure of the contact 79 of micro-switch 72.At a 5 psi. lower pressure than occurred to effect operation of themicro-switch 72, the micro-switch 71 will function to energize the coil108 of protective relay 102 and effect closure of the contacts 109 andopening of the normally-closed contacts 110, 111. Thus, the closing ofthe normally-open contacts 79 of micro-switch 72 at the higher pressurewill result in immediate actuation of the alarm circuits including alarmelements 93, 94. This will give the station attendant warning that alowering of pressure within the interrupting unit 1 is present.

At 5 pounds per square inch lower pressure than the pressure conditionwhich caused micro-switch 72 to function, micro-switch '71 will closethe contacts 78 thereof resulting in energization of the auxiliary relay102. This will do two things. First, it will open up the closing circuitto the X relay. Secondly, it will open up the tripping circuit to thetrip coil 47.

If the utility customer desires an automatic tripping of the circuitinterrupter 1 at the lower pressure setting which caused micro-switch 71to operate, the transfer switch 96A may be closed and this will resultin tripping the tripping device 47. More specifically, the automatictripping circuit for the tripping solenoid 47 comprises ground terminal68, auxiliary contacts 67 of mechanism 26, tripping coil 47, terminal166, contacts1tl9 of Z relay (which are now closed) closed contacts 98of trans-fer switch 96A, to positive terminal 95. Thus, an automatictripping of the circuit breaker 1 will take place at the lower pressure.As mentioned, the conditions set up in FIG. 3 are for the purpose ofenabling a utility customer to open up the closing circuit only at thelower pressure and not at the higher pressure, as was the conditionwhich existed in the FIG. 1 control diagram.

It will be noted that in FIG. 1, with the transfer switch 96 closed thenormally open contact 78 of micro-switch '71, when closed bylow-pressure conditions would have to carry the current suffieient toenergize the tripping coil 47. This current is appreciable. In case thecontacts 73, 78 of microswitch 7 1 of the pressure switch of FIG. 1 arenot capable of having capacity to close the tripping circuit to thetripping coil 47 an auxiliary protective relay 86, as shown in FIG. 4may be employed.

With reference to FIG. 4, it will be noted that the pressure-controlcircuit is in many respects similar to that of FIG. 1. However, upon adrop of pressure within the casing 3 of the circuit interrupter .1, thisdrop of pressure will be reflected .Within a container 81 to cause aclosing of the contacts 73, 117. This will energize the coil 118 of theSG protective relay. The closing circuit for the coil 118 of the SGrelay includes connection 119 to the negative terminal 58 and throughconnection 126 to the positive terminal 41. Closure of the SG relay willeffect closing of the contacts 121 and 122 with a consequent opening ofthe contacts 123. With the transfer switch 963 in the open position, asshown in FIG. 4, closing of the SG relay upon a drop of pressure willopen up the tripping circuit 124 to the tripping switch CST. This willprevent tripping the breaker open upon such a drop of pressure.

Actuation of the pressure switch 125 causing separation of the contacts'73, 126 will open up the closing circuit 127 to the X relay, preventingthereby closing of the breaker 1 upon a drop of pressure.

Should it be desired toeffect an automatic tripping of the breaker itopen in the event of a drop of pressure, then the transfer switch 963will be closed. In such an eventuality, it will be noted that closing ofthe contacts 73, 117 of the pressure switch 125 upon a drop of pressurewill energize the coil 47 of the latch release 48 to effect opening ofthe breaker 1 by a circuit which includes connection 127, contacts 122of S6 relay (now closed) contacts 128 of transfer switch 963 and COEI1Ction 12%) to the positive terminal 4 1.

From the foregoing, it will be apparent that there has been provided animproved pressure control circuit for controlling the proper operationof the breaker 1 by utilization of only a single pressure switch 70, 125for obtaining many control functions. The three functions enumeratedabove, namely energizing an alarm circuit, opening the closing controlcircuit of the operating mechanism, and opening the tripping circuit, orautomatically tripping the breaker open, has been provided by a singlepressure switch. There results considerable simplification and costsaving. In addition, by minimizing the number of parts employed, thenumber of component parts which may individually cause trouble has beendiminished.

Although there has been illustrated and described specific structuresand control circuits therefor, it is to be clearly understood that thesame were merely for the purpose of illustration, and that changes andmodifications may readily be made therein by those skilled in the artWithout departing from the spirit and scope of the invention.

I claim as my invention:

1. A gas-type circuit interrupter including a casing filled with anarc-extinguishing gas, a pair of separable contacts disposed within saidcasing in the ambient of said enclosed gas, the interrupting integrityof the gas-type circuit interrupter being dependent upon the pressure ofsaid enclosed gas, a single pressure switch responsive to the pressureof the gas Within said casing and having independent dual contactstructure actuated thereby, an operating mechanism for operating saidseparable contacts, circuit means for said operating mechanism includinga closing coil and a tripping coil, a closing relay for energizing saidclosing coil, said independent dual contact structure associated withsaid single pressure switch having normally closed contacts in serieswith the circuit for said closing relay under normal pressurizedcondition of said casing, said independent dual contact structure in addition having normally closed contacts in series with said trippingcoil, said pressure switch functioning to open both said pairs ofnormally-closed contacts upon a hazardous drop of pressure, whereby adrop of pressure within said casing to a dangerous state will open saidindependent dual normally closed contacts to prevent closing andtripping of the gas-type circuit interrupter.

2. A gas-type circuit interrupter including a casing filled with anarc-extinguishing gas, a pair of separable contacts disposed within saidcasing in the ambient of said enclosed gas, the interrupting integrityof the gas-type circuit interrupter being dependent upon the pressure ofsaid enclosed gas, a single pressure switch responsive to the pressureof the gas within said casing and having independent dual contactstructure actuated thereby, an operating mechanism for operating saidseparable contacts, circuit means for said operating mechanism includinga closing coil and a tripping coil, a closing relay for energizing saidclosing coil, said independent dual contact structure associated withsaid single pressure switch having first normally closed contacts inseries with the circuit for said closing relay under normal pressurizedcondition of said casing, said independent dual contact structure inaddition having second normally closed contacts in series with saidtripping coil, an alarm circuit including an alarm element, normallyopen contacts associated with said first normally-closed contactstructure for sounding an alarm upon drop of pressure within saidcasing, aid pressure switch functioning to open both first and secondnormallyclosed contacts and close said normally open contacts upon ahazardous drop of pressure, whereby a drop of pressure within saidcasing to a dangerous state will open said normally closed contacts toprevent closing and tripping of the gas-type circuit interrupter andalso actuate said alarm element.

3. A gas-type circuit interrupter including a casing filled with anarc-extinguishing gas, a pair of separable contacts disposed within saidcasing in the ambient of said enclosed gas, the interrupting integrityof the gas-type circuit interrupter being dependent upon the pressure ofsaid enclosed gas, a single pressure switch responsive to the pressureof the gas within said casing and having independent dual contactstructure actuated thereby, said dual contact structure including twopairs of first and second normallyclosed contacts actuated at differentpressure settings of the pressure switch, an operating mechanism foroperating said separable contacts, circuit means for said operatingmechanism including a closing coil and a tripping coil, a closing relayfor energizing said closing coil, the first normally closed contactsopened at the higher pressure setting upon dropping pressure being inseries with the circuit for said closing relay, the other secondnormally closed pair of contacts opened at the lower pressure settingupon dropping pressure being in series with said tripping coil, saidpressure switch functioning to open both first and second normallyclosed contacts upon a hazardous drop of pressure, whereby a drop ofpressure within said casing to a dangerous state will first open saidfirst normally-closed contacts in series with the closing relay toprevent closing and upon a further drop of pressure the other secondpair of contacts will open to prevent tripping of the gas-type circuitinterrupter.

4. A gas-type circuit interrupter including a casing filled with anarc-extinguishing gas, a pair of separable contacts disposed within saidcasing in the ambient of said enclosed gas, the interrupting integrityof the gas-type circuit interrupter being dependent upon the pressure ofsaid enclosed gas, a single pressure switch responsive to the pressureof the gas within said casing and having independent dual contactstructure actuated thereby, an operating mechanism for operating saidseparable contacts, circuit means for said operating mechanism includinga closing coil and a tripping coil, a closing relay for energizing saidclosing coil, said independent dual contact structure associated withsaid single pressure switch having first normally closed contacts inseries with the circuit for said closing relay under normal pressurizedcondition of said casing, said dual contact structure in addition havingsecond normally closed contacts in series with said tripping coil, analarm circuit including an alarm element, normally open contactsassociated with said first normallyclosed contact structure for soundingan alarm upon drop of pressure within said casing, said pressure switchfunctioning to open both first and second normally-closed contacts andclose said normally open contacts upon a hazardous drop of pressure,whereby a drop of pressure within said casing to a dangerous state willopen said first and second normally closed contacts to prevent closingand tripping of the gas-type circuit interrupter, and said normally opencontacts of the pressure switch closing at a higher differentialpressure setting than said second normally closed contacts associatedwith the tripping circuit.

5. The combination in a gas-type circuit interrupter of a housingcontaining an arc-extinguishing gas under pressure, a movable contactseparable from a relatively stationary contact to establish an arcwithin said gas under pressure, a single pressure switch having asensing gas connection with said housing for sensing the pressureconditions therein, the pressure switch having an independent pair ofsingle-pole double-throw micro-switches actuated thereby, an operatingmechanism for operating the movable contact including a closing coil anda tripping coil, a closing relay for energizing said closing coil, afirst normally closed contact of one of the micro-switches being inseries with said closing relay, a second normally closed contact of theother micro-switch being in series with the circuit of the trippingcoil, said pressure switch functionin g to open both said pairs ofnormally-closed contacts upon a hazardous drop of pressure, whereby adrop of pressure within said casing to a dangerous state will open saidnormally closed contacts to prevent closing and tripping of the gas-typecircuit interrupter.

6. The combination in a gas-type circuit interrupter of a housingcontaining an arc-extinguishing gas under pressure, a movable contactseparable from a relatively stationary contact to establish an arewithin said gas under pressure, a single pressure switch having asensing gas connection with said housing for sensing the pressureconditions therein, the pressure switch having an independent pair ofsingle-pole double-throw micro-switches actuated thereby, an operatingmechanism for operating the movable contact including a closing coil anda tripping coil, a closing relay for energizing said closing coil, 21first normally closed contact of one of the micro-switches being inseries with said closing relay, a second normally closed contact of theother micro-switch being in series with the circuit of the trippingcoil, said pressure switch functioning to open both said pairs ofnormally-closed contacts upon a hazardous drop of pressure, whereby adrop of pressure within said casing to a dangerous state will open saidnormally closed contacts to prevent closing and tripping of the gas-typecircuit interrupter, means providing an alarm circuit, and a normallyopen contact associated with the first normally-closed contact of thefirst said micro-switch being in series with said alarm circuit forsounding an alarm upon a drop of housing pressure.

7. The combination in a gas-type circuit interrupter of a housingcontaining an arc-extinguishing gas under pressure, a movable contactseparable from a relatively stationary contact to establish an arewithin said gas under pressure, a single pressure switch having asensing gas con nection with said housing for sensing the pressureconditions therein, the pressure switch having an independent pair ofsingle-pole double-throw micro-switches actuated thereby, an operatingmechanism for operating the movable contact including a closing coil anda tripping coil, a closing relay for energizing said closing coil, afirst normally closed contact of one of the micro-switches being inseries with said closing relay, a second normally closed contact of theother micro-switch being in series with the circuit of the trippingcoil, said pressure switch functioning to open both said pairs ofnormally-closed contacts upon a hazardous drop of pressure, whereby adrop of pressure within said casing to a dangerous state will open saidfirst and second normally closed contacts to prevent closing andtripping of the gas-type circuit interrupter, means providing an alarmcircuit, a normally open contact associated with the firstnormally-closed contact of the first said micro-switch being in serieswith said alarm circuit for sounding an alarm upon a drop of housingpressure, and means for actuating the two micro-switches at differentpressure settings.

8. A gas-type circuit interrupter including a casing filled with anarc-extinguishing gas, a pair of separable contacts disposed within saidcasing in the ambient of said enclosed gas, the interrupting integrityof the gas-type circuit interrupter being dependent upon the pressure ofsaid enclosed gas, a single pressure switch responsive to the pressureof the gas within said casing and having contact structure actuatedthereby, an operating mechanism for operating said separable contacts,circuit means for said operating mechanism including a closing coil anda tripping coil, a closing relay for energizing said closing coil, saidcontact structure associated with said single pressure switch havingfirst and second independent normally open contacts, a protective relayenergized by closure of said second normally open contacts, saidprotective relay when deenergized having normally closed contacts inseries with said closing coil, an alarm circuit connected in series withsaid first pair of normally open contacts, said pressure switchfunctioning to close both pairs of normally-open contacts upon ahazardous drop of pressure, the first and second pair of normally opencontacts having different pressure responses, whereby the alarm circuitwill be energized prior to an opening of the closing circuit upondropping pressure.

9. A gas-type circuit interrupter including a casing filled with anarc-extinguishing gas, a pair of separable contacts disposed within saidcasing in the ambient of said enclosed gas, the interrupting integrityof the gas-type circuit interrupter being dependent upon the pressure ofsaid enclosed gas, a single pressure switch responsive to the pressureof the gas within said casing and having contact structure actuatedthereby, an operating mechanism for operating said separable contacts,circuit means for said operating mechanism including a closing coil anda tripping coil, a closing relay for energizing said closing coil, saidcontact structure associated with said single pressure switch havingnormally closed contacts in series with the circuit for said closingrelay under normal pressurized condition of said casing, said contactstructure in addition having normally open contacts, a protective relayfor energizing said tripping coil, said normally open contacts beingconnected to energize said protective relay, said pressure switchfunctioning to open the normally-closed contacts and to close thenormally-open contacts upon a hazardous drop of pressure, wherebyactuation of the pressure switch upon a drop of easing pressure willopen the circuit to the closing coil and energize the protective relayto trip the circuit interrupter open.

References Cited by the Examiner UNITED STATES PATENTS 2,766,404 10/56Ashenden 31722 2,911,492 11/59 Beatty 200-148 X 2,937,320 5/60 Easley 3l722 SAMUEL BERNSTEIN, Primary Examiner.

1. A GAS-TYPE CIRCUIT INTERRUPTER INCLUDING A CASING FILLED WITH ANARC-EXTINGUISHING GAS, A PAIR OF SEPARABLE CONTACTS DISPOSED WITHIN SAIDCASING IN THE AMBIENT OF SAID ENCLOSED GAS, THE INTERRUPTING INTEGRITYOF THE GAS-TYPE CIRCUIT INTERRUPTER BEING DEPENDENT UPON THE PRESSURE OFSAID ENCLOSED GAS, A SINGLE PRESSURE SWITCH RESPONSIVE TO THE PRESSUREOF THE GAS WITHIN SAID CASING AND HAVING INDEPENDENT DUAL CONTACTSTRUCTURE ACTUATED THEREBY, AN OPERATING MECHANISM FOR OPERATING SAIDSEPARABLE CONTACTS, CIRCUIT MEANS FOR SAID OPERATING MECHANISM INCLUDINGA CLOSING COIL AND A TRIPPING COIL, A CLOSING RELAY FOR ENERGIZING SAIDCLOSING COIL, SAID INDEPENDENT DUAL CONTACT STRUCTURE ASSOCIATED WITHSAID SINGLE PRESSURE SWITCH HAVING NORMALLY CLOSED CONTACTS IN SERIESWITH THE CIRCUIT FOR SAID CLOSING RELAY UNDER NORMAL PRESSURIZEDCONDITION OF SAID CASING, SAID INDEPENDENT DUAL CONTACT STRUCTURE INADDITION HAVING NORMALLY CLOSED CONTACTS IN SERIES WITH SAID TRIPPINGCOIL, SAID PRESSURE SWITCH FUNCTIONING TO OPEN BOTH SAID PAIRS OFNORMALLY-CLOSED CONTACTS UPON A HAZARDOUS DROP OF PRESSURE, WHEREBY ADROP OF PRESSURE WITHIN SAID CASING TO A DANGEROUS STATE WILL OPEN SAIDINDEPENDENT DUAL NORMALLY CLOSED CONTACTS TO PREVENT CLOSING ANDTRIPPING OF THE GAS-TYPE CIRCUIT INTERRUPTER.